feat(core, websockets): Effects output stream

[JozefFlakus]

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

[...] response interceptor to modify certain type of responses for various reasons. Such as when Accept header is application/vnd.api+json, so maybe there is a stream of outgoing message which can be use to adjust the response accordingly. The API endpoint should worry only about resource being worked on. The exact data sent over wire or its representation is orthogonal to the API endpoint. Or in other case, when RouteEffect sends 404 as a status code. It will be intercepted by common code that will send appropriate message depending upon the Accept header.
@mistyharsh <<

Issue Number: #83

What is the new behavior?

The API design shouldn't define any sort of additional post-Effect middlwares. In order to have a consistent API and preserve stream-like nature of the framework, each listener (HTTP, WebSockets) should expose an additional output stream where the developer can adjust the outputted EffectResponse accordingly to the needs.

HTTP:

const httpServer = httpListener({
  middlewares: [ ... ],
  effects: [ ... ],
  output$: out$ => out$.pipe(
    // intercept Effect response and adjust it to your needs accordingly ☺️
  ),
});

WebSockets:

const webSocketServer = webSocketListener({
  middlewares: [ ... ],
  effects: [ ... ],
  output$: out$ => out$.pipe(
    // intercept Effect response and adjust it to your needs accordingly ☺️
  ),
});

Does this PR introduce a breaking change?

[ ] Yes
[x] No

[codecov]

Codecov Report

Merging #96 into next will not change coverage.
The diff coverage is 100%.

@@         Coverage Diff         @@
##           next    #96   +/-   ##
===================================
  Coverage   100%   100%           
===================================
  Files        76     76           
  Lines       957    961    +4     
  Branches     85     85           
===================================
+ Hits        957    961    +4

Impacted Files	Coverage Δ
packages/core/src/http.interface.ts	100% <ø> (ø)	⬆️
...s/core/src/response/responseContentType.factory.ts	100% <100%> (ø)	⬆️
packages/core/src/listener/http.listener.ts	100% <100%> (ø)	⬆️
...ages/websockets/src/listener/websocket.listener.ts	100% <100%> (ø)	⬆️

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